Assembly is simple if all one does is printing hello world (even that is actually not trivial, because one needs to know/read the syscall and the ABI).
Anything beyond that gets complex quickly, in one way or another. On simple architectures, like the 6502, even doing a simple division is complex (heck, even additions are verbose, since 8 bits are too few for a lot of operations). On more complex architectures, like x64, there is a monstrous ISA full of inconsistencies.
Learning assembly as in learning an instruction set also doesn't include a lot of details of computer architecture, although at least some modern assembly books mix both domains.
Anything beyond that gets complex quickly, in one way or another. On simple architectures, like the 6502, even doing a simple division is complex (heck, even additions are verbose, since 8 bits are too few for a lot of operations). On more complex architectures, like x64, there is a monstrous ISA full of inconsistencies.
Learning assembly as in learning an instruction set also doesn't include a lot of details of computer architecture, although at least some modern assembly books mix both domains.